Apparatus and process for burning fuel



Feb. 28, 1928. 1,660,831

E. w. CLARKE APPARATUS AND `PROCESS FOR BURNING FUEL Filed Oct.` 1.3. 1922 -3 Sheets-Sheet 3 'Patented Feb. 28,1928.

UNITED STATES;

. 1,660,831 v; PATENT. OFFICE.

EDGAR CLARKE, OF EVANSTON, ILLINOIS,` ASSIGNOR TO AMERICAN` TAR PRODUCTS COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE.

APPARATUS AND PROCESS FOR BURNING FUEL.

'Application ledvOctober 13, 1922.` Serial No. 594,380.

' The object of this invention is to accomplish the employment as commercial fuel of pitch and otheranalogous carbonaceous materials which melt orliquefy when subjected initially to furnace temperatures.

In` the distillation` of tar for the production of chemical products and creosote, there vremains a residue constituted essentially of pitch, which residue comprises about fifty to seventy per centum of the original tar mass pitch have'accumulated at the tar distil-y leries. Attempts have'been'made to employ this surplus pitch as fuel by liquefying it and introducing it in a liquid state into the combustion chamber by burners analogous to those employed for fuel oil. Although pitch is high in carbon and; chemicallyis a most excellent fuel, the employment of pitch in the liquid state as a. substitute for 3 fuel oil has not met with success, because of the difficulties and complications encountered in maintaining the pitch in a Huid state at the required temperature. It -has also been proposed to pulverize the pitch and employ it as a substitute for pulverized coal in pulverized coal burners. But the prior attempts to employ pulverized pitch in existing burner devices have not been successful, for the reason that the section of the pipe or burner delivering the pitch into the furnace became heated by radiation from the furnace, with the/result that temperatures were ldeveloped that softened and made particles of pulverized pitch to adhere to the inner surface of the delivery pipe or burner.

mulation of a coke-like mass which seriously interfered with the delivery -of the pulverized fuel to the furnace and eventually completely choked up the burner or delivery pipe.` By the`prese`nt invention, the employment of pulverized pitch as fuel is succesfully accomplished without permitting the pitch to soften or melt in the delivery nozzle or pipe, so that accumulations which This action resulted in the accuthe firebox communicates wlth the main! choke the nozzle are altogether eleminated and a continuous delivery of the pitch to the furnace may be effected. l

In addition 'to the general objects recited above, the invention has for further objects such other improvements or advantages in operation and results as may be-l found to obtain in the structures and processes hereinafter described or claimed.

In the accompanying drawings forming a 0l part of this specification and showingfor purposes of exemplification a preferred form and manner in which the invention may be embodied and practiced, in conjunction with one well known type of furnace construction, but without limiting the `claimed invention specifically to such illustrative instance:

Figure 1 is a vertical section taken longitudinally through a furnace of ordinary construction equipped with means for burning powdered pitch as fuel, constructed in accordance with the present invention.

Figure 2 is a horizontal section ,of the parts illustrated in Fig. 1.

Figure 3 is an enlarged vertical section of the nozzle and fuel delivery portion at the front of the furnace.

Figure 4 is a horizontal section of the parts shown in Fig. 3.

In its present embodiment, the invention is applied to an ordinary type of furnace. For convenience, the present description will be confined to the illustrated application. of the invention to such a furnace. Features of the invention are, however, applicable generally to furnace structures; consequently, the invention is not confined in its scope to the specific use and embodiment herein described as an illustrative example. 95

Referring to the drawings, there are illustrated views of a furnace of ordinary construction. The furnace is constituted of the usual main heating chamber 11, located beneath the boiler 12, and the front irebox 13 100 in which the fuel is burned. ,At its rear end,

heating chamber 11 and, atits bottom, with the ash pit 14. The front wall 15 of the frebox is provided with a stoke hole 16 105 through which the fuel isintroduced into the firebox. Preferably, the top of the Stoke hole 16 inclines upwardly toward the interior of the iirebox, as shown at 17 in Figs. 1 and 3, and.the side walls diverge 110 toward the interior, as shown at 18 in Fi s. 2 and 4. This construction provides a sto e hole in the front refractory wall of the furnace which is flared toward the firebox, so as to prevent impingement of an of the particles of solid fuel with the wa ls of the stoke hole, as said fuel particles pass into the firebox. The front of the Stoke hole 16 is provided with a vertical plate 19 having a central inlet opening 20 made large enough to permit thevjet of fuel to pass, without in'- terference, into the firebox. In applying the invention to existing installations, the ordinary stoke hole door may serve as the vertical plate for the front of the Stoke hole, by simply boring a hole in the door large enough to admit the jet of fuel.

According to the invention, the powdered pitch is delivered into the furnace, from a nozzle or nozzles, the delivery end of which terminates at a distance from the front face of the front wall of the furnace, so that the nozzle is located out of the zone of high temperature and overheating 4of the nozzleis avoided. The pitch is delivered by the nozzle in a stream at high velocity through the inlet 20 and stoke hole 16, the velocity being maintained high enough to. keep the fuel in a compact stream until it reaches the combustion zone within the firebox, thus preventing the fuel from coming in contact with any part of the furnace at the point of entrance to which it might adhere ifbsuch contact be made. In other words, the fuel is introduced into the furnace at such a velocity that the particles will have reached the combustion zone in the irebox before the heat of the furnace can become effective to cause the particles to melt and adhere to the nozzle, or furnace surfaces. Consequently, any probability of the delivery nozzle becoming choked from agglomerated pitch or pitch coke deposits is practically eliminated. Moreover, as the lnozzle is located entirely beyond the front wall of the furnace and out of the zone of high temperature, the delivery end of the nozzle is kept continuously below the melting point of the pitch. But even if the nozzle did become overheated, from long continued use, the velocity of the fuel stream would be Great enough to carry the fuel into the iire ox without deposits on the wall of the nozzle. Y

As shown in theY drawings, the fuel delivery nozzle 21'is preferablyv sharply tapered toward the delivery end so asr to cause the powdered pitch to issue from the spout 22 in `a jet or stream of great force and confined laterally of the jetfor a sufficient distance to keep the fuel stream compact until it reaches the combustion zone, so as to avoid impingement of the fuel particles with any part of the furnace structure at the `point of entrance of the fuel.

The lpowdered pitch is delivered to the nozzle 21 through a fuel pipe 23 and the fuel stream may be an admixture of powdered fuel with combustion supporting air or other gases. The fuel inlet 20 in the front of the furnace may be made large enough to permit the jet of fuel to draw along with -it into the furnacey suflicient air to support combustion of the fuel.

Any suitable means for imparting the high velocity to the fuel stream is within the purview of the invention. Mechanical devices or blowers having the requisite capacity may be employed. The drawing shows a pulverizer 24, thev delivery end of which is connected to the fuel pipe 23, the pulverizer operating not only to pulverize the fuel but also to mix it with air for effecting efficient combustion and to deliver the -admixture of pulverized fuel and combustion supporting air at high velocity through the pipe 23 to the nozzle 21. The sharply tapered nozzle 21v and its spout 22, which is greatly restricted in diameter in respect to the diameter of the ipe 23, serve to accelerate the alreadyhig velocity Stream of fuel in the pipe 23, so thata powerful jet issues fromthe spout 22. The lump pitch may be deposited in the hopper 25 and conveyed by a chute 2G from the hopper to the inlet of the pulverizer.

In carrying out the present invention it lhas been found that a satisfactory operation of the furnace is obtained by employing from 50.to 60 cubic feet of air per pound of pitch, and a minimum jet velocity of 3000 feet per minute has served to maintain the pulverized pitch in suspension and prevent its becoming adherent prior to its reaching the combustlon zone. It will be understood however, that a satisfactory operation of the furnace may be obtained by varying thesev proportions and employing higher jet yelcities at the point of entrance of the The term pitch as employed in the fore-- may be variously embodied within the scope l of the claims hereinafter I claim: 1.-The method of feeding made.

ulverized pitch to a furnace which consists 1n feeding l the pulverized pitch in a stream of such velocity that the fuel is maintained in a compact stream at the point of entrance into the furnace, releasing the fuel from its feeding means while the fuel is outside of the furnace, and entraining a surrounding annulus of air with said stream, whereby the fuel reaches the combustion zone before it can become adherent, substantially as specified.

2. Apparatus for burning pulverized pitch comprising, in combination: a furnace having an unenclosed fuel inlet in its front wall; means including a nozzle for lfeeding such pitch in a blast through said nozzle to said furnace, said means and said nozzle beng located entirely outside of said furnace and positioned with respect to the inlet in the front wall of the furnace so that the delivery end of said nozzle terminating opposite said fuel inlet is on the outside of the front wall of said furnace and at a substantial distance from the outer surface of the said front Wall and with a vertically extending free space-therebetween; whereby the pitch being ejected from said nozzle is by such air-space insulated from being rendered sticky by the furnace heat until after such pitch is projected through said inlet.

3. Apparatus for burning pulverize'd pitch comprising, in combination: a furnace having an unenclosed fuel inlet in its front wall; means including a delivery nozzle fory feeding such pitch in a blast through said nozzle to said furnace; said means and said nozzle being located entirely outside said furnace and positioned with respectto the fuel inlet in the front wal-l of the furnace so that the delivery end of said nozzle opposite the fuel inlet does not extend to the plane of the outer surface of the front wall of the furnace and does not extend into 'the fuel inlet; whereby the pitch being ejected from said nozzle is by such air-space insulated'from being rendered sticky by the furnace heat until after such pitch is projected through said inlet.

4. In the feeding of pulverized pitch to a furnace the improvement whichv consists 1n: y

delivering it with a blast atlthe point of entrancel into said furnace at such a velocity as to maintain the stream against dispersing while entering said furnace, and releasing the stream from its feeding means while the pitch is outside of the outer surface of the furnace Wall and substantially insulated therefrom` by an. air-space; whereby the pitch leaves the feeding means at aregion where the temperature from radiation is not high enough to effect adherence to the feeding means of particles of pitch thatare still within the feeding means.

In testimony whereof I have hereunto set my hand.

EDGAR W. CLARKE. y 

